1. Field of the Invention
This invention relates to a system for treating waste water and, more particularly, to an oil and grease skimmer employed in an oxidation ditch clarifier.
2. Prior Art
To remove impurities, such as sugars and other carbohydrates and proteins and other forms of nitrogen, as well as other types of pollutants from domestic sewage, industrial waste water or similar waste water streams, the use of an orbital or oxidation ditch system can be employed.
In its general usage, an orbital waste water treatment system includes an elongated tank having two sidewalls and at least one partition wall mounted vertically in the tank substantially parallel to the two sidewalls and spaced apart from the ends of the tank to form an endless, circuitous channel or oxidation ditch to contain a portion of the waste water stream. In a conventional oxidation ditch system, the waste water is constantly circuitously flowed in the ditch while at the same time aerated to provide oxygen for micro-organisms to decompose most of the pollutants. An example of such a system can be seen in U.S. Pat. No. 3,846,292, wherein a portion of the waste water put in the ditch is removed after aeration and then transferred to a conventional clarifier where heavier solid particles are separated out. Because of high construction costs, a system employing the clarifier in the ditch was developed; an example of which is seen in U.S. Pat. No. 4,303,516.
However, because of turbulence in the clarifier used as well as the cost of ditch and clarifier construction due to the use of settlement separation processes, even these systems were not as efficient as desired. This led to the development of improved clarifier designs as shown in applicant's U.S. Pat. Nos. 362,625 and 4,383,922, identified above. This invention relates to the improved process of treating waste water streams made possible by these improved clarifier designs and, more particularly, improved skimmers to remove oils, greases and other floating particles from the clarifier even when the level of fluids in the oxidation ditch and clarifier change.